Image publishing systems are widely used to distribute images from a centralized server computer connected to a network to users that are also connected to the network. The images are generated by an image source and stored in a centralized database connected to the server computer. Users at client computers make requests for images to the server computer. The server computer, in response to the requests, sends image data over the network to the user at the client computer.
Image publishing systems can be used in numerous fields and disciplines including, for example, the medical field. The image publishing systems used by the medical field, and particularly hospitals, utilize specialized hardware and software to store, distribute and view medical related image data. A medical image publishing system is termed a Picture Archiving and Communication System (PACS).
A typical PACS system includes one or more imaging sources, an archive or image database and multiple viewing stations. Typical image sources include X-ray, computerized tomography (CT) scans, nuclear medicine images, ultrasound and magnetic resonance imaging (MRI). The images, once generated, are stored on a centralized storage device. Users can then request to view the images on their viewing stations. Requested images first have to be located in the archive, retrieved and transmitted to the user's client computer.
Users are typically connected to the PACS server computer over a communications network. The network may be a local area network (LAN) or a wide area network (WAN) such as the Internet. Currently, the data rate for a typical LAN network connection is relatively fast, e.g., 100 Mbps using Fast Ethernet (FE). Even higher data rates of Gigabit Ethernet (GE) at 1 Gbps are becoming increasingly common in LANs. WAN connections, however, typically have much slower data rates. Although high data rate WAN connections, e.g., broadband connections, are becoming increasingly common, many users still communicate over slow speed WAN connections, e.g., 64 kbps or less using modems.
Since typical medical images, e.g., radiological images, are relatively large files, e.g., tens of megabytes, it would take a relatively long time to transmit entire images to users located remotely from the centralized PACS server and connected using slow speed communications.
A disadvantage of a conventional PACS system is that image distribution is performed manually. An image source generates an image where it is stored on an image archive or storage facility connected to the server. Once it is stored, a user, e.g., physician, at a viewing station or client computer must manually request to view the image. The client computer generates a request and sends it to the PACS server. In response to the request, the server retrieves the image from the image database and transmits it to the client computer. A problem arises in that many times, users do not know when an image becomes available for viewing. There is typically a lag between the time when the image is actually available and the time when the user is aware of this fact and requests the image to be transferred. This is inefficient in terms of time since a physician, for example, would typically like to be able to view the images as soon at they are available.
A further disadvantage is that a conventional PACS system requires a user to wait until the entire image is successfully received before the image can be viewed. In the case of an emergency, a physician would not want to wait for the radiology images to be transmitted in their entirety from a PACS server.
The problems discussed above are compounded when considering that in the medical field, physicians work with radiological studies and not with individual images. A study is a collection of data comprising anything that may be useful to the physician viewing the data. Examples of the contents of studies include one or more radiological images (CT scan, MRI, ultrasound, etc. of various body parts), text files containing medical histories, medical opinions from other physicians, laboratory test results, etc.
Conventional PACS systems perform medical image transfer by sending the entire study data from the image storage location to the user's client workstation. Depending on bandwidth availability, and compression ratios, this may take hours to complete over a slow network connection, e.g., dial-up line, creating a tradeoff between speed of delivery and degree of image quality. Further, the contents of a study cannot be viewed until the entire study is completely received by the client computer or viewing station. In the case of a large study, this is inefficient and undesirable because the physician must wait for the entire contents of a study to be received before being able to view any of the images within the study.
Therefore, there is a need for an image publishing system with improved distribution over slow WAN communication connections. It is desirable that such a system provides some form of data pushing whereby studies (or images) are immediately sent to users automatically once they become available on the server. It is also desirable that the image publishing system has the capability of overcoming the limitation imposed by slow WAN connections. It is further desirable that the image publishing system permits users to view the contents of a study or image before data transmission for that study or image is complete.